Quantitative single-exposure laser speckle contrast imaging
23 Oct 2018-Vol. 10820, pp 35-42
TL;DR: In this paper, a modified velocity computing approach incorporating the effects of scattering events and other experimental parameters was proposed to obtain a relatively inexpensive LSCI system with near real-time results.
Abstract: Laser speckle contrast imaging (LSCI) is a well-established blood flow imaging technique, through the computed whole field contrast map. Though LSCI offers high spatial and temporal resolution, accurate quantification of blood flow remains a challenge. In this paper, we demonstrate a single exposure system, introducing a modified velocity computing approach incorporating the effects of scattering events and other experimental parameters to result in a relatively inexpensive LSCI system with near real time results. Parameters like vessel dimension and concentration of scattering centers are cumulatively represented by defining the number of scattering events in the region of interest (ROI). The number of scattering events is considered along with the decorrelation time in deducing flow velocity. We present a modified equation for velocity computation incorporating the effects of scattering centers. This work attempts to bring consistency in flow velocity calculation across different samples to achieve a robust single exposure LSCI system. The LSCI setup was calibrated based on a system dependent constant, which was found to be a linear function of flow velocity, to predict velocity quantitatively. We present the results of the developed system on standard micron-sized flow channels.
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TL;DR: The underlying physics of speckle contrast imaging is reviewed, recent developments to improve the quantitative accuracy of blood flow measures are discussed and applications in neuroscience, dermatology and ophthalmology are reviewed.
Abstract: First introduced in the 1980s, laser speckle contrast imaging is a powerful tool for full-field imaging of blood flow. Recently laser speckle contrast imaging has gained increased attention, in part due to its rapid adoption for blood flow studies in the brain. We review the underlying physics of speckle contrast imaging and discuss recent developments to improve the quantitative accuracy of blood flow measures. We also review applications of laser speckle contrast imaging in neuroscience, dermatology and ophthalmology.
918 citations
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TL;DR: In this article, the velocity distribution in a flow field is mapped on the photograph as variations in speckle contrast, which can be converted to intensity variations by means of a simple spatial filtering technique.
641 citations
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TL;DR: Recent clinical research that employs DCS-measured CBF as a biomarker of patient well-being, and as an indicator of hemodynamic and metabolic responses to functional stimuli, is described.
410 citations
"Quantitative single-exposure laser ..." refers methods in this paper
...Though Ultrasound Doppler flowmetry and LDF encourage continuous monitoring of blood flow, they only provide single point measurement....
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...Currently used non-invasive imaging modalities for visualization and analysis of blood flow include Positron emission tomography (PET), Single photon emission computed tomography (SPECT), Arterial spin-labeled magnetic-resonance imaging (ASL-MRI), Xenon computed tomography, Ultrasound Doppler flowmetry, and Laser Doppler flowmetry (LDF) [2]....
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TL;DR: In this paper, a multispeckle dynamic light scattering technique is proposed to resolve the motion of scattering sites in cases that this motion changes systematically with time, based on the visibility of the speckle pattern formed by the scattered light as detected by a single exposure of a digital camera.
Abstract: We describe a multispeckle dynamic light scattering technique capable of resolving the motion of scattering sites in cases that this motion changes systematically with time. The method is based on the visibility of the speckle pattern formed by the scattered light as detected by a single exposure of a digital camera. Whereas previous multispeckle methods rely on correlations between images, here the connection with scattering site dynamics is made more simply in terms of the variance of intensity among the pixels of the camera for the specified exposure duration. The essence is that the speckle pattern is more visible, i.e., the variance of detected intensity levels is greater, when the dynamics of the scattering site motion is slow compared to the exposure time of the camera. The theory for analyzing the moments of the spatial intensity distribution in terms of the electric-field autocorrelation is presented. It is tested for two well-understood samples, a colloidal suspension of Brownian particles and a coarsening foam, where the dynamics can be treated as stationary and hence can be benchmarked by traditional methods. However, our speckle-visibility method is particularly appropriate for samples in which the dynamics vary with time, either slowly or rapidly, limited only by the exposure time fidelity of the camera. Potential applications range from soft-glassy materials, to granular avalanches, to flowmetry of living tissue.
350 citations
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TL;DR: A new Multi-Exposure Speckle Imaging (MESI) instrument that has potential to obtain quantitative baseline flow measures and a new speckle model which can discriminate flows in the presence of static scatters is presented.
Abstract: Laser Speckle Contrast Imaging (LSCI) is a minimally invasive full field optical technique used to generate blood flow maps with high spatial and temporal resolution. The lack of quantitative accuracy and the inability to predict flows in the presence of static scatterers such as an intact or thinned skull have been the primary limitation of LSCI. We present a new Multi-Exposure Speckle Imaging (MESI) instrument that has potential to obtain quantitative baseline flow measures. We show that the MESI instrument extends the range over which relative flow measurements are linear. We also present a new speckle model which can discriminate flows in the presence of static scatters. We show that in the presence of static scatterers the new model used along with the new MESI instrument can predict correlation times of flow consistently to within 10% of the value without static scatterers compared to an average deviation of more than 100% from the value without static scatterers using traditional LSCI. We also show that the new speckle model used with the MESI instrument can maintain the linearity of relative flow measurements in the presence of static scatterers.
311 citations